Submariner Date: Oystersteel, Cerachrom and the Oyster case

Rolex uses Oystersteel for its steel cases — a 904L-family alloy developed for its corrosion resistance and lustre. The Cerachrom bezel insert is virtually scratch-proof and its colour unaffected by UV; the numerals are coated with a thin layer of platinum by PVD. The Oyster case, screw-down crown and Triplock system give the Submariner Date its 300 m rating.